J. C. Sit – Research – Publications: Uniformity

Overview

A classic problem for physical vapour deposition (PVD) is the non-uniformity of the process, arising from the combination of system geometry and source emission anisotropy.  This has major implications for both research and manufacturing, where control of the thin film’s structure and therefore properties is of great interest.  While convention thin film deposition systems can somewhat optimise deposition thickness uniformity, generally through schemes that compensate for geometric variation (e.g., by substrate holder rotation), the geometry problem is substantially more complex for oblique- or glancing-angle deposition, especially when taking substate motion into account.  In this work, our main aim was to elucidate this problem.

This paper is the culmination of an extensive study on the thickness and density uniformity of thin films fabricated by oblique- and glancing-angle deposition.  We present a generalised, geometric framework applicable to low-pressure PVD onto substrates of arbitrary size and in arbitrary position and orientation.

The following article appeared in J. Appl. Phys. and may be found at http://aip.scitation.org/doi/10.1063/1.3559748.

• N. G. Wakefield and J. C. Sit,
  On the uniformity of films fabricated by glancing angle deposition,
  Journal of Applied Physics 1098, 084332/1–10 2011. 10.1063/1.3559748

Abstract

Films fabricated using the glancing angle deposition technique are subject to significant variations in several important film parameters across a sample due to geometric conditions that are not uniform across the substrate.  This paper presents a method to quantify the non-uniformities in these quantities, starting from a generalized geometric framework, for low-pressure, physical vapor deposition of thin films on substrates of arbitrary size and position.  This method is applicable to any glancing angle deposition setup including substrate tilt and rotation but focuses on the case of constant deposition angle and arbitrary azimuthal rotation.  While some quantities, such as the effective deposition angle and the deposited mass per unit area at any given point on the substrate can be determined purely from the geometry of the deposition setup, obtaining further quantities, such as the film density and thickness, requires additional, material-specific information that is easily measured.

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